Major and minor metabolites of cocaine in human plasma following controlled subcutaneous cocaine administration

Cocaine is rapidly metabolized to major metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME), and minor metabolites, norcocaine, p-hydroxycocaine, m-hydroxycocaine, p-hydroxybenzoylecgonine (pOHBE), and m-hydroxybenzoylecgonine. This IRB-approved study examined cocaine and metabolite plasma concentrations in 18 healthy humans who provided written informed consent to receive low (75 mg/70 kg) and high (150 mg/70 kg) subcutaneous cocaine hydrochloride doses. Plasma specimens, collected prior to and up to 48 h after dosing, were analyzed by gas chromatography-mass spectrometry (2.5 ng/mL limits of quantification). Cocaine was detected within 5 min, with mean ± SE peak concentrations of 300.4 ± 24.6 ng/mL (low) and 639.1 ± 56.8 ng/mL (high) 30-40 min after dosing. BE and EME generally were first detected in plasma 5-15 min post-dose; 2-4 h after dosing, BE and EME reached mean maximum concentrations of 321.3 ± 18.4 (low) and 614.7 ± 46.0 ng/mL (high) and 47.4 ± 3.0 (low) and 124.4 ± 18.2 ng/mL (high), respectively. Times of last detection were BE > EME > cocaine. Minor metabolites were detected much less frequently for up to 32 h, with peak concentrations ≤ 18 ng/mL for all analytes except pOHBE (up to 57.7 ng/mL). These data improve our knowledge of the pharmacokinetics of cocaine and its major and minor metabolites in plasma following controlled subcutaneous cocaine administration.